More info to make it clearer: The 'relay denied' I wrote in my previous is not in smtp.example.com logs.
E-mail from u...@example.com to u...@example.com : ------ client (1) --> server1.example.com (2) --> smtp.example.com (3) --> server1.example.com (4) ------ The 'relay denied' message is on server1.example.com logs at step (4). I can solve the 'relay denied' by changing main.cf at server1.example.com from: ------ smtpd_relay_restrictions = permit_sasl_authenticated, defer_unauth_destination ------ to: ------ mynetworks = IP_address_for_smtp.example.com smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination ------ But then I have an infinitive loop: ------ client --> server1.example.com --> smtp.example.com --> server1.example.com --> smtp.example.com --> server1.example.com --> smtp.example.com --> ... ------ I think the only way to fix this is to have 2 postfix instances, right? One for incoming and one for outgoing.
